Paternity is a biological construct. Royal intermarriage has been practiced by ruling dynasties since times immemorial. It had often been observed that this l

Paternity is a biological construct. Royal intermarriage has been practiced by ruling dynasties since times immemorial. It had often been observed that this leads to problems and infertility, and indeed this is the root cause for the incest taboos that you find in varying forms and shapes in most cultures and religions. However, it has only been with the rise of modern biology and genetics in the 20th century, that this practice was abandoned. Speaking of Ancient Rome, it has been speculated that the decline of the Roman Empire was in parts caused by the failure of the ruling families to produce enough children. Naturally, we don't have enough information today to confirm or disprove such speculation. I have no idea why you link to an article about the Mosuo. It has no bearing on the biological nature of paternity.